There are probably a couple of reasons:
1. they are angry at someone who “did them wrong,” who was a Christian.
2. There are plenty examples of false prophets, liars and cheats, or poor scholars of the gospel, who are in the Christian church leadership who they can point to and say “see, all Christians are bad.”
It is a tough message to counter and very difficult to turn them.
As we used to say in the Marine Corps, “There are no atheists in foxholes.”.......................